This invention relates in general to circuits for amplifying signals and, more particularly, relates to circuits which are useful in audio systems having more than one audio output channel wherein the audio signal can be remotely controlled.
Variable gain circuits controlled by a continuous voltage are widely used for volume controls, as for instance, in a television receiver. The use of such circuits is desirable because the audio signal does not pass through a control potentiometer which may be located some distance from the signal processing circuits thereby avoiding radiation problems generally associated with the coupling wires from the control potentiometer to the signal processing circuit. However, certain disadvantages exist with some of the circuits used in the past such as having outputs which do not have the same return reference as the input signal thereby requiring a level shifting circuit. Another disadvantage is that some of the prior art circuits do not have the proper gain response so that the balance and volume control of an audio signal can not be combined in the same circuit. If a combination of volume and balance control of an audio system having more than one audio channel were made possible the result would be reduced circuitry in a stereo or quadraphonic system.
Accordingly, one of the objects of the present invention is to provide an improved amplifier.
Another object of the present invention is to provide an electronic amplifier circuit having a logarithmic gain response and providing an output having the same return reference as an input signal.
Yet another object of the present invention is to provide a circuit capable of simultaneously amplifying at least two signals and providing gain control for the at least two signals as well as balance control between the at least two signals.
A further object of the invention is to provide a monolithic integrated circuit capable of amplifying a plurality of signals and having the capability of being remotely controlled.